I say this because some ungodly people have wormed their way into your churches, saying that God’s marvelous grace allows us to live immoral lives. The condemnation of such people was recorded long ago, for they have denied our only Master and Lord, Jesus Christ. – Jude 1:4

From Jesus to the apostles, Peter, Paul, Jude and a host of Old Testament prophets, the Bible is filled with warnings to the people of God about false prophets. Some may ask, why would the Lord warn us against false teachers when the true believer is eternally secure in Christ?  False teaching cannot destroy the Church of Jesus Christ, since Jesus Himself has promised that He will build His Church and the gates of hell will not prevail against it (Matthew 16:18), false teaching can however, hurt the body of Christ, cause Christ’s name to be blasphemed and cause Christianity to be maligned and evil spoken of.

So how do we recognize false teachers? The Bible shows us how. Here are some (some words in the verses have been emphasized):

 2 Peter 2:1-3, 14, 18-19

But false prophets also arose among the people, just as there will also be false teachers among you, who will secretly introduce destructive heresies, even denying the Master who bought them, bringing swift destruction upon themselves. Many will follow their sensuality, and because of them the way of the truth will be maligned;
and in their greed they will exploit you with false words; their judgment from long ago is not idle, and their destruction is not asleep. having eyes full of adultery that never cease from sin, enticing unstable souls, having a heart trained in greed, accursed children;
For speaking out arrogant words of vanity they entice by fleshly desires, by sensuality, those who barely escape from the ones who live in error, promising them freedom while they themselves are slaves of corruption; for by what a man is overcome, by this he is enslaved.

Jude 1:4, 8, 12, 16

For certain persons have crept in unnoticed, those who were long beforehand marked out for this condemnation, ungodly persons who turn the grace of our God into licentiousness and deny our only Master and Lord, Jesus Christ.
Yet in the same way these men, also by dreaming, defile the flesh, and reject authority, and revile angelic majesties.
These are hidden reefs at your love feasts, as they feast with you without fear, shepherds feeding themselves; waterless clouds, swept along by winds; fruitless trees in late autumn, twice dead, uprooted;
These are grumblers, malcontents, following their own sinful desires; they are loud-mouthed boasters, showing favoritism to gain advantage.

I will point out a few characteristics of false teachers from these two passages. This is not by any means an exhaustive list. 

that we may avoid being led away, we must seek to grow in all grace, in faith, and virtue, and knowledge. Labor to know Christ more clearly, and more fully; to know him so as to be more like him, and to love him better. – Matthew Henry

 
 
From both of these passages and many others in scripture, we learn that false teachers:

Work within the church. They are usually among believers. They came in “secretly” that means they pretended to be the true but are not.

 “Secretly” introduce a false teaching. This means they take a truth of scripture and twist it to suit their purposes. For example, no verse in the Bible has been more abused than the Matthew 7:1 where Jesus says “Judge not that you be not judged”. Both false teachers and their adherents have abused and twisted this verse to the extent of saying it means one can never address the sin of others within the church.

False teachers always encourage sexual sins and immorality. Peter says many will follow their sensuality. Jude says they turn the grace of God into licentiousness. As the NLT puts it false teachers have “wormed their way into your churches, saying that God’s marvelous grace allows us to live immoral lives.” Nothing can be further from the truth.

Are Greedy. – They are covetous, materialistic and money minded.

Deny the Lordship of Christ. – This means they preach “easy believism”. The preaching that you can “accept Christ” and still live anyway you want. Claiming that as long as you have prayed a prayer or walked an aisle you are saved, even if nothing changes in your life. They also deny the deity of Christ and in some cases deny the virgin birth out right.

Are Arrogant. It should not surprise us that false teachers are arrogant since pride is the root of all sins. Jude compares false teachers to the fallen angels who followed after lucifer in his rebellion against God out of pride and that like fallen angels, God as reserved for false preachers, an eternal damnation.

Like I said, this is not an exhaustive list of characteristics of false teachers, but we get the idea.   The question then is, how can a believer guard against false teaching? Simple, get to know Christ through His word. We are to grow and increase in our knowledge of God through His word.

Peter tells in 2 Peter 3:18 that we “must grow in the grace and knowledge of our Lord and Savior Jesus Christ.”

False teachers can be likened to counterfeiters who make counterfeit money. The best guard against being deceived into taking counterfeit money is to spend time getting to know the real thing so you are able to spot a counterfeit a mile away. This is essentially what Peter is saying in the verse above. We must grow in the grace & knowledge of Christ.

Matthew Henry summarized it as follows:

Those who are led away by error, fall from their own steadfastness. And that we may avoid being led away, we must seek to grow in all grace, in faith, and virtue, and knowledge. Labor to know Christ more clearly, and more fully; to know him so as to be more like him, and to love him better. This is the knowledge of Christ, which the apostle Paul reached after, and desired to attain; and those who taste this effect of the knowledge of the Lord and Savior Jesus Christ, will, upon receiving such grace from him, give thanks and praise him, and join in ascribing glory to him now, in the full assurance of doing the same hereafter, forever. him, and join in ascribing glory to him now, in the full assurance of doing the same hereafter, forever.

 
 
Soli Deo Gloria!